Consumers desire attractive and easy to install and operate window coverings. Additionally, energy conservation has spurred interest in improving the insulating efficiency of window coverings.
Venetian-type blinds are the most popular window coverings. This is due in large measure to their ability to control light penetration, viewing area and privacy without raising or lowering the blinds or slats. This is accomplished by a ladder-like supporting device suspended between a headrail and footrail which includes a pair of vertical string-like members connected together by spaced apart rungs, typically made out of fabric. The string-like members are spaced apart at a distance approximately equal to the width of the individual slats and thereby abut against the outside edges of the slats. As one of the pair of strings is raised and the other is lowered the rungs that support the slats tilt causing the support slates to tilt in unison.
Venetian-type blinds are also provided with a cord for raising or lowering the footrail which serves to raise or lower the slats. This cord is affixed to the footrail and passes through aligned elongated holes in each of the slats. As the cord is pulled, the footrail rises causing the slats to sequentially stack on the footrail.
Venetian-type blinds of such construction are disadvantageous for several reasons. Because the string-like members abut against the outside edges of the slats, adjacent slats are prevented from coming together as the string-like members are raised and lowered. A pathway therefore exists at all times between adjacent slats and through the holes in the slats used for the string-like members and the raising and lowering cord. This pathway permits the unwanted transmission of light, heat and sound thereby compromising the insulating properties of the window covering. In addition, venetian blinds accumulate dust and grime which is particularly difficult to remove in the area where the string-like members gather or bunch on the outside edges of the slats.
Thus, venetian-type blinds do not provide the combination of viewing, privacy and insulating properties necessary to satisfy the demand for energy conserving window coverings.